In our previously studies, cerebral vasospasm was experimentally produced by the canine two-hemorrhage model. 12-Lipoxygenase metabolites of the arachidonic acid, 12-hydroxyeicosatetraenoic acid (HETE), was mainly detected as a amount of about 2 nmol/ g wet weight in the subarachnoid clot by reversed-phase High-Performance Liquid chromatography (HPLC). This arachidonate 12-lipoxygenase metabolite was presumably formed rightly after blood clotting in the subarachnoid space by 12-lipoxygenase originated from platelets and leukocytes. We also investigated 5-lipoxygenase activity of basilar arteries with vasospasm in the same model. Twenty to one hundred fold of 5-HETE was produced in the vessels with vasospasm, compared with untreated ones. Moreover, leukotriene B_4 and C_4 were detected in the spasm arteries, but not in the control ones. This activation of 5-lipoxygenase pathway in the spasm arteries was due to the intrinsic 5-lipoxygenase of the vessels, which was stimulated by 12-Hydro
… Moreperoxyeicosatetraenoic acid (HPETE), the precursor of 12-HETE, since leukocytes (rich sources of 5-lipoxygenase) were rarely found in the microscopic observation. These results led us to carry out the experiment to see whether the cisternal injection of 12-HPETE could cause the delayed cerebral vasospasm or not.12-HPETE and 12-HETE were synthesized from arachidonic acid by partially purified porcine leukocyte 12-lipoxygenase, and purified using straight-phase HPLC. The injection of 12-HPETE (0.5 mg) into the canine cisterna magna caused a delayed onset of cerebral vasospasm that lasted long. 12-HPETE in CSF was rapidly reduced to 12-HETE, which was also disappeared within 6 hours after cisternal injection. And then, intrathecal arteries began to contract. This contraction continued for 5 or 6 days. This phenomenon mimicked the cerebral vasospasm as shown in the one-hemorrhage model in our previous experiment. 12-HETE (0.5 mg) injected into CNS had much less potency to induce cerebral vasospasm. We substantiated that 12-HETE was contained in the subarachnoid clot. 12-HPETE is a possible initiator of the delayed cerebral vasospasm. Furthermore, the cisternal injection of 15-HPETE and 13-hydroperoxyoctadecadienoic acid (hydroperoxide of linoleic acid) also successfully caused delayed cerebral vasospasm. Lipid peroxides should be convincing candidates for the initiators of that.次に、12ーHPETE(0.5mg)を犬大槽内に注入すると8時間以上のライムライを持ち、3〜5日持続する脳血管攣縮を作製し得た(自家動脈血一回髄注モデルに匹敵する)。12ーHETE(0.5mg)注入では、軽度の遅発性の収縮を認めたにすぎなかった。また、髄注した12ーHPETEは、髄液内で急速に12ーHETEに代謝され、12ーHETE自体も3時間で髄液中より消失していた。in vitvoにおける12ーHPETEの半減期を考慮すると髄腔内には、12HPETEを能動的に代謝・吸収する系の存在が示唆されるとともに、12ーHPETEは、遅発性脳血管攣縮の誘発物質であって、維持には関与していないものと考えられた。更に、血管攣縮誘発作用が、アラキドン酸の過酸化物(12ーHPETE15ーHPETE)に特異的なものなのか、あるいは、脂質の過酸化物一般に認められる作用であるのかを検討するため、リノ-ル酸の過酸化(13HPOD 0.5mg)髄注した。13ーHPOD注入により12ーHPETEより収縮は弱いが、むしろ長期間(2週間)持続する遅発性脳血管攣縮を作製し得た。このことより、遅発性脳血管攣縮の誘発作用は、脂質過酸化物一般に認められる作用である可能性が示唆された。 Less